This invention relates to a climbing device for vehicles comprising a number of foot steps arranged on a frame composed of one or more supporting members which are made of flexible material in order to allow temporary deformation of the frame without causing permanent damages therein if striking an obstacle. Such a climbing device, which is advantageously used in connection with tractors, earth moving scrapers and similarly high vehicles, is previously known by the U.S. Pat. No. 3,887,216 which discloses a device comprising one single foot step and two supporting bodies in the form of portions of a single rubber strap. These supporting members are of rectangular cross sectional shape providing a greater resistance to bending perpendicularly to a plane through the device than parallel to said plane in order to make said members yield easier for strains acting laterally on the device than for strains acting perpendicularly to the plane of the device. When examined in the latter direction only, each supporting member is however as apt to yield inwardly towards the vehicle as it is apt to yield outwardly therefrom. In practice this means that the foot step rather easily moves inwardly towards the vehicle when a person gets up on it and thereby the climbing operation is felt unpleasant and unsafe. Such inward movement may also injure the legs and knees of the climbing person in question.
A climbing device consisting of a single foot step and two supporting chains is further known by the British Pat. No. 1,485,929. Also in this case the supporting members are as apt to yield inwardly towards the vehicle as outwardly therefrom. As a matter of fact the supporting chains of this device is equally yieldable in all directions.
It is an object of the present invention to eliminate the disadvantages of the prior art devices and provide a climbing device or ladder which guarantees a safe and steady climbing at the same time as the frame or the supporting members of the device are free to yield in those directions which are essential in order not to damage said members when striking an obstacle. According to one aspect of the invention this is achieved by the fact that the supporting member in question comprises a reinforcement located in the vicinity of that face of the member which is directed outwardly from the vehicle in order to provide said member with a greater resistance to bending in the direction of the vehicle than in the opposite direction.
According to another aspect of the invention each foot step arranged between two parallel, preferably long supporting members is pivotally connected at the opposite ends thereof to brackets mounted in the supporting members. By this pivotal connection no detrimental breaking movements are transferred from the foot step to the supporting members when the frame as a whole is deflected upon striking the ground or the obstacle.